In terms of, for example, increasing the energy density of a secondary battery, research and development are performed on a high-voltage type non-aqueous electrolyte secondary battery whose operation voltage is increased. As an electrolyte that can be used in the high-voltage type non-aqueous electrolyte secondary battery, for example, a liquid electrolyte that contains a support salt (non-aqueous electrolyte, hereinafter also referred simply to as an “electrolyte”) is known.
As a technology on the non-aqueous electrolyte secondary battery described above, for example, Patent Literature 1 discloses an organic electrolyte battery in which an organic electrolyte is interposed between a positive electrode material and a negative electrode material, and in which at least a part of the surface of the positive electrode active material particles of the positive electrode is coated with an adhesion substance which is not easily oxidized even by the supply of oxygen from the positive electrode active material and which has ion conductivity and electron conductivity. Paragraph [0045] of the specification in Patent Literature 1 describes an example where a mixture of LiNi0.5Mn1.5O4 and Li3PO4, a conductive material and an ion conductive binder are put into a solvent and are agitated, and are thereafter applied on a collector and are dried and then the positive electrode is produced. Patent Literature 2 discloses a lithium-ion secondary battery that uses an electrolytic solution containing a non-aqueous solvent, a support salt and an SEI formation material. Paragraph [0024] of the specification in Patent Literature 2 discloses LiNi0.5Mn1.5O4 as an example of the positive electrode active material preferably used, and paragraph [0043] discloses that the surface of the positive electrode active material particles is coated with Li3PO4. Patent Literature 3 discloses a lithium battery that includes a cathode electrode containing a porous conductive material whose surface is coated with a sulfa and/or a sulfa-containing organic compound.